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WO2020004097A1 - Capteur à ultrasons - Google Patents

Capteur à ultrasons Download PDF

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Publication number
WO2020004097A1
WO2020004097A1 PCT/JP2019/023823 JP2019023823W WO2020004097A1 WO 2020004097 A1 WO2020004097 A1 WO 2020004097A1 JP 2019023823 W JP2019023823 W JP 2019023823W WO 2020004097 A1 WO2020004097 A1 WO 2020004097A1
Authority
WO
WIPO (PCT)
Prior art keywords
matching layer
acoustic matching
ultrasonic sensor
adhesive
piezoelectric element
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2019/023823
Other languages
English (en)
Japanese (ja)
Inventor
昌道 橋田
知樹 桝田
賢輝 信長
永原　英知
祐大 石崎
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Panasonic Intellectual Property Management Co Ltd
Original Assignee
Panasonic Intellectual Property Management Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Panasonic Intellectual Property Management Co Ltd filed Critical Panasonic Intellectual Property Management Co Ltd
Priority to CN201980042135.5A priority Critical patent/CN112313968A/zh
Priority to EP19826265.1A priority patent/EP3813385A4/fr
Priority to US17/057,085 priority patent/US20210208111A1/en
Publication of WO2020004097A1 publication Critical patent/WO2020004097A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0644—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element
    • B06B1/0662—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface
    • B06B1/067—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface which is used as, or combined with, an impedance matching layer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/28—Details, e.g. general constructional or apparatus details providing acoustic coupling, e.g. water
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/24—Probes
    • G01N29/2437—Piezoelectric probes
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/02—Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H04R17/02—Microphones

Definitions

  • the present invention mainly relates to a sensor that transmits and receives ultrasonic waves.
  • a piezoelectric element is generally made of ceramics (having a high density and a high speed of sound), and the density and sound speed of a gas such as air to which ultrasonic waves are transmitted are determined by the density of the ceramic and the speed of sound. Significantly smaller. Therefore, the efficiency of energy transfer from the piezoelectric element to the gas becomes very low.
  • measures have been taken to increase the energy transfer efficiency by interposing an acoustic matching layer between the piezoelectric element and the gas that has lower acoustic impedance than the piezoelectric element and higher acoustic impedance than the gas.
  • Z1 acoustic impedance of the piezoelectric element
  • Z2 acoustic impedance of the acoustic matching layer
  • Z3 acoustic impedance of the transmitted object (gas).
  • the ultrasonic wave propagating through the acoustic matching layer deforms the acoustic matching layer, so that the energy of the ultrasonic wave is dissipated as heat. Therefore, the material used as the acoustic matching layer must be hardly deformed (having a large elastic modulus).
  • the acoustic impedance Z2 of the acoustic matching layer needs to be significantly smaller than the acoustic impedance of the solid in order to approach the acoustic impedance Z3 of the gas.
  • a substance having a small acoustic impedance has a low sound speed and a low density, and is generally a substance that is easily deformed in many cases. For these reasons, few materials satisfy the characteristics required for the acoustic matching layer.
  • the acoustic impedance of the solid-state piezoelectric element differs from that of the gas by about five orders of magnitude
  • the acoustic impedance of the acoustic matching layer needs to be reduced by about three orders of magnitude to the acoustic impedance of the piezoelectric element in order to satisfy Equation (1). Therefore, there are few substances that satisfy the characteristics of the acoustic matching layer.
  • the acoustic impedance of the piezoelectric element and the first acoustic matching layer (the first acoustic matching layer) and the acoustic impedance of the first acoustic matching layer and the second acoustic matching layer (the second acoustic matching layer (transmitted object)) can be improved.
  • the ultrasonic wave is transmitted with sufficient efficiency by using the fact that the transmission efficiency becomes highest when the expression (1) is satisfied between the acoustic impedance of the second layer and the gas in the acoustic impedance, and the expression (1) is satisfied. Attempts have been made to make it happen.
  • the first acoustic matching layer is preferably made of a hard (high elastic modulus) material that reduces energy loss due to deformation in order to efficiently transmit ultrasonic waves to the second acoustic matching layer.
  • a hard material such as Ketone (polyetheretherketone) is desirable.
  • a candidate having excellent characteristics as an acoustic matching layer is a resin having a large elastic modulus.
  • examples of the resin having a large elastic modulus include super engineering plastics such as PEEK, and these resins are also hardly adherent resins.
  • the acoustic matching layer when a hard resin is used as the acoustic matching layer, there is a possibility that peeling may occur particularly near the center. Further, when the acoustic matching layer is provided with a through-hole having a diameter of a considerable degree or more, there is a possibility that the performance as an ultrasonic sensor may be reduced due to a reduction in ultrasonic waves.
  • An ultrasonic sensor includes at least a piezoelectric element, a first acoustic matching layer bonded to the piezoelectric element, and an adhesive bonding the piezoelectric element and the first acoustic matching layer.
  • the ultrasonic sensor according to the present disclosure provides an anchor effect by integrating the adhesive that bonds the piezoelectric element and the first acoustic matching layer and the adhesive that is solidified in the gap, and has excellent durability. Can be obtained.
  • the acoustic matching layer is bonded to the piezoelectric element or a metallic member bonded to the piezoelectric element to secure electric conductivity.
  • the piezoelectric element is generally made of ceramics such as lead zirconate titanate.
  • the objects to be bonded in the ultrasonic sensor of the present disclosure are hard-to-adhesive resins and ceramics or metals that are relatively easily bonded.
  • the acoustic matching layer is provided with a void communicating with the opening, so that the adhesive that has been cured after filling into the void is combined with the acoustic matching layer by chemical bonding, mechanical bonding, that is, by the anchor effect. Joined.
  • the facing surface of the adhesive is relatively easily bonded to ceramics or metal.
  • the piezoelectric element and the acoustic matching layer are firmly joined, so that even when stress is generated due to a difference in coefficient of thermal expansion between them, an ultrasonic sensor having excellent durability is not easily separated. Can be provided.
  • the acoustic matching layer has an opening that opens to the bonding surface and a gap that communicates with the opening, the acoustic matching layer and the adhesive can obtain a strong bond by the anchor effect. Therefore, even when the acoustic matching layer is made of a material having poor adhesion, strong bonding to the piezoelectric element can be obtained.
  • a hard resin having excellent properties as an acoustic matching layer for example, a super engineering plastic such as PEEK is difficult to obtain and obtain, but it can be used as an acoustic matching layer by performing strong bonding with a piezoelectric element by an anchor effect. it can.
  • an ultrasonic sensor having excellent characteristics and reliability can be provided.
  • FIG. 1 is a schematic sectional view of the ultrasonic sensor according to the first embodiment.
  • FIG. 2 is a schematic cross-sectional view of the ultrasonic sensor according to the second embodiment.
  • FIG. 3 is a top view of the first acoustic matching layer according to the second embodiment.
  • FIG. 4 is a schematic sectional view of an ultrasonic sensor according to the third embodiment.
  • FIG. 5 is a top view of the first acoustic matching layer according to the third embodiment.
  • FIG. 6A is a schematic cross-sectional view of an ultrasonic sensor showing another example of the first embodiment.
  • FIG. 6B is a schematic cross-sectional view of an ultrasonic sensor showing another example of the first embodiment.
  • FIG. 6C is a schematic sectional view of an ultrasonic sensor showing another example of the first embodiment.
  • FIG. 1 is a schematic cross-sectional view of the ultrasonic sensor according to the first embodiment.
  • the ultrasonic sensor 1 has a piezoelectric element 2, an adhesive 3, a case 4, a first acoustic matching layer 5, a second acoustic matching layer 6, and electrodes 7a and 7b.
  • the case 4 is a bottomed cylindrical metal member.
  • the piezoelectric element 2 is bonded to the first surface 4 b inside the top surface 4 a, which is a flat plate portion of the case 4, with a conductive adhesive 9.
  • a first acoustic matching layer 5 is bonded to a second surface 4 c outside the top surface 4 a of the case 4 with an adhesive 3 so as to face the piezoelectric element 2.
  • a second acoustic matching layer 6 is bonded to the surface of the first acoustic matching layer 5 not facing the case 4 with an adhesive 3.
  • the electrode 7a is connected to the electrode 2a of the piezoelectric element, and the electrode 7b is connected to the case 4.
  • the piezoelectric element 2 Since the electrode 2b of the piezoelectric element is bonded to the case 4 with the conductive adhesive 9, the piezoelectric element 2 oscillates by applying a predetermined voltage between the electrodes 7a and 7b, and emits ultrasonic waves. The generated ultrasonic waves are finally transmitted to the gas via the case 4, the first acoustic matching layer 5, and the second acoustic matching layer 6.
  • the case 4 has a bottomed cylindrical shape, but may have a flat plate shape.
  • the first acoustic matching layer 5 has a plurality of openings 8 a on a surface facing the case 4, and a wedge shape or a cross-sectional area parallel to the joint surface with the case 4 becomes smallest near the opening 8 a.
  • a truncated cone-shaped space 8 is provided continuously to each opening 8a.
  • the gap 8 is filled with the liquid adhesive 3 in advance, and the surface having the opening 8a of the first acoustic matching layer 5 and the case are filled with the adhesive 3 filled in the gap 8 in a wet state.
  • the case 4 and the first acoustic matching layer 5 are joined by bringing the second surface 4c of the case 4 into contact directly or via the adhesive 3 applied between them, and the adhesive 3 is solidified.
  • the piezoelectric element 2 Since the characteristic required for the ultrasonic sensor 1 is to transmit the ultrasonic waves generated by the piezoelectric element 2 to the gas with high efficiency, the piezoelectric element 2, the case 4, the first acoustic matching layer 5, and the second acoustic matching layer It is necessary to join the six spaces while securing sufficient strength and environmental durability.
  • the bonding of the piezoelectric element 2 and the case 4, the case 4 and the first acoustic matching layer 5, and the joining of the first acoustic matching layer 5 and the second acoustic matching layer 6 are as follows.
  • the piezoelectric element 2 is generally made of ceramics, and the case 4 is generally made of metal. Since both ceramics and metals are relatively easy to bond, and ceramics and metals have relatively similar coefficients of thermal expansion, their joining is relatively easy.
  • the first acoustic matching layer 5 is made of resin and the second acoustic matching layer 6 is often made of resin, the first acoustic matching layer 5 and the second acoustic matching layer 6 have similar thermal expansion coefficients. Adhesion is relatively easy.
  • the case 4 is often made of metal and the first acoustic matching layer 5 is often made of resin, and it is general that the case 4 and the first acoustic matching layer 5 have significantly different coefficients of thermal expansion. Furthermore, the resin forming the first acoustic matching layer 5 is highly likely to be hardly adhered to by PEEK or the like, and may be separated from the adhesive 3 at the interface.
  • an element necessary for efficiently transmitting ultrasonic waves from the piezoelectric element 2 to the gas is to establish a bond between the adhesive 3 and the first acoustic matching layer 5.
  • the adhesive cured inside the gap 8 cannot pass through the opening 8a.
  • An anchor effect is obtained, and the bonding between the adhesive 3 and the first acoustic matching layer 5 becomes strong. Therefore, the adhesive 3 and the first acoustic matching layer 5 are not easily separated from each other even if a shearing force due to the difference in the coefficient of thermal expansion acts between the adhesive 3 and the first acoustic matching layer 5.
  • the shape of the gap 8 is a wedge shape or a truncated cone shape, but it goes without saying that the gap 8 may have a cross-sectional area larger than the opening cross-sectional area of the opening 8a. There is no.
  • the ultrasonic sensor 1 has the configuration including the case 4 and the second acoustic matching layer 6.
  • a configuration not using the second acoustic matching layer as in the ultrasonic sensor 31 shown in FIG. 6A a configuration not using the case as in the ultrasonic sensor 41 shown in FIG. 6B, or an ultrasonic sensor 51 shown in FIG. 6C.
  • various configurations can be implemented without departing from the gist of the present disclosure.
  • FIG. 2 is a schematic sectional view of the ultrasonic sensor according to the second embodiment
  • FIG. 3 is a top view of the first acoustic matching layer shown in FIG. 2, and a broken line shown in FIG. Indicates the position.
  • the ultrasonic sensor 11 includes a piezoelectric element 2, an adhesive 3, a case 4, a first acoustic matching layer 15, a second acoustic matching layer 6, and electrodes 7a and 7b.
  • the components denoted by the same reference numerals as those described in the embodiment have the same configurations as the components in the first embodiment, and the description is omitted.
  • the ultrasonic sensor 11 of the present embodiment is different from the ultrasonic sensor 1 of the first embodiment in the structure of the first acoustic matching layer 15.
  • the cavity 18 of the first acoustic matching layer 15 is cylindrical, and a resin is injection-molded as a through hole penetrating from the surface facing the case 4 to the surface facing the second acoustic matching layer 6. It is manufactured by.
  • the case 4, the first acoustic matching layer 15, and the second acoustic matching layer 6 fill the gap 18 with the liquid adhesive 3 in advance, and the case 4, while the adhesive 3 is wet.
  • the first acoustic matching layer 15 and the second acoustic matching layer 6 are overlapped.
  • the case 4, the first acoustic matching layer 15, and the second acoustic matching layer 6 are joined by solidifying the adhesive 3.
  • the adhesives on both surfaces of the first acoustic matching layer 15 are bonded via the adhesive 3 filled in the through holes that are the gaps 18, a strong anchor effect is obtained, and the adhesive 3 And the first acoustic matching layer 15 are firmly bonded.
  • the gap 18 (through hole) of the first acoustic matching layer 15 may be formed by injection molding of a resin, or may be formed by machining a metal disk.
  • FIG. 4 is a schematic sectional view of the ultrasonic sensor according to the third embodiment
  • FIG. 5 is a top view of the first acoustic matching layer shown in FIG.
  • the ultrasonic sensor 21 includes a piezoelectric element 2, an adhesive 3, a case 4, a first acoustic matching layer 25, a second acoustic matching layer 6, and electrodes 7a and 7b.
  • the same components as those described in the embodiments indicate the same configuration, and the description will not be repeated.
  • the ultrasonic sensor 21 according to the present embodiment is different from the ultrasonic sensor 1 according to the first embodiment in the structure of the first acoustic matching layer 25.
  • the first acoustic matching layer 25 is made porous by applying pressure while heating a resin powder.
  • the space that is not filled with the powder corresponds to the gap 28 of the first acoustic matching layer 25.
  • the opening of the void 28 is formed from the powder disposed near the outermost surface, and the void 28 has at least one or more portions having an area equal to or greater than the opening. is there.
  • the case 4 In a state where the liquid adhesive 3 is filled in the gap 28 having such a characteristic, the case 4, the first acoustic matching layer 25, and the second acoustic matching layer 6 are overlapped and the wet adhesive 3 is spread. By solidifying, it is possible to realize a strong bonding and to provide an ultrasonic sensor having excellent reliability.
  • a method of forming the void 28 (porous) of the first acoustic matching layer 25 it is also possible to mold the metal powder by applying pressure while heating.
  • a reference ultrasonic sensor is installed at a position 100 mm away from the ultrasonic sensor evaluated in each embodiment, and the ultrasonic wave emitted from the ultrasonic sensor evaluated in each embodiment is The electromotive force that propagates to the reference sensor and is generated in the reference sensor is used.
  • a disc-shaped lead zirconate titanate having a thickness of 3.8 mm and a diameter of 10 mm was used as a piezoelectric element, and a 0.2 mm-thick SUS304 sensor was used as a case. Further, only one acoustic matching layer having a thickness of 1.2 mm and a diameter of 10 mm obtained by adding a glass balloon to an epoxy resin to have a density of 0.5 g / cm 3 was used.
  • the characteristics of the ultrasonic sensor used in each embodiment can be known from the electromotive force generated from the reference ultrasonic sensor.
  • the adhesive strength of the ultrasonic sensor is obtained by dividing the electromotive force after the thermal shock test by the electromotive force before the thermal shock test, and the larger the value (sensitivity retention rate), the better the adhesive strength. .
  • a disk-shaped lead zirconate titanate having a thickness of 3.8 mm and a diameter of 10 mm was used.
  • the adhesive 3 an epoxy adhesive which is liquid at normal temperature and solidifies by heating is used.
  • a case 4 made of SUS304 having a thickness of 0.2 mm was used.
  • the first acoustic matching layer 15 is made of PEEK resin having a thickness of 1 mm and a diameter of 10 mm.
  • the opening on the surface on the case 4 side has a diameter of 300 ⁇ m, and the opening on the surface on the second acoustic matching layer 6 has a through hole of 400 ⁇ m. What was molded as 8 was used. The distance between the holes is 100 ⁇ m on the side where the diameter of the opening is 400 ⁇ m.
  • a polymethacrylimide resin is foamed to form a molded article composed of closed cells, and a molded article having a density of 0.07 g / cm 3 is formed into a disc having a thickness of 0.8 mm and a diameter of 10 mm. The processed one was used.
  • the assembly of the ultrasonic sensor 11 was performed as follows. First, the first acoustic matching layer 15 is immersed in the adhesive 3 at room temperature, and the case 4, the first acoustic matching layer 15, and the second acoustic matching layer 6 are arranged in this order from below. A load of 100 g was applied. In this state, the adhesive 3 is spread between the first acoustic matching layer 15 and the case 4 and between the first acoustic matching layer 15 and the second acoustic matching layer 6.
  • the adhesive 3 is solidified by heating at 150 ° C. for 60 minutes, and the second acoustic matching layer 6 is joined from the case 4. Further, the case 4 and the piezoelectric element 2 were joined by a conductive adhesive, and the case 4 and the electrode 7b, and the piezoelectric element 2 and the electrode 7a were joined by solder.
  • the electromotive force of the ultrasonic sensor manufactured as described above was 100 mV, and the electromotive force of the ultrasonic sensor after the thermal shock test was 98 mV. Therefore, the sensitivity retention rate of the ultrasonic sensor was 98%.
  • a disk-shaped lead zirconate titanate having a thickness of 3.8 mm and a diameter of 10 mm was used.
  • the adhesive 3 an epoxy adhesive which is liquid at normal temperature and solidifies by heating is used.
  • a case 4 made of SUS304 having a thickness of 0.2 mm was used.
  • the first acoustic matching layer 15 was made of PEEK resin having a thickness of 1 mm and a diameter of 10 mm, and a through-hole having a diameter of 300 ⁇ m was formed as a gap 18. The distance between the holes is 100 ⁇ m.
  • a polymethacrylimide resin is foamed to form a molded article composed of closed cells, and a molded article having a density of 0.07 g / cm 3 is formed into a disc having a thickness of 0.8 mm and a diameter of 10 mm. The processed one was used.
  • the assembly of the ultrasonic sensor 11 was performed as follows. First, the first acoustic matching layer 15 is immersed in the adhesive 3 at room temperature, and the case 4, the first acoustic matching layer 15, and the second acoustic matching layer 6 are arranged in this order from below. A load of 100 g was applied. In this state, the adhesive 3 is spread between the first acoustic matching layer 15 and the case 4 and between the first acoustic matching layer 15 and the second acoustic matching layer 6.
  • the adhesive 3 is solidified by heating at 150 ° C. for 60 minutes, and the second acoustic matching layer is joined from the case 4. Further, the case 4 and the piezoelectric element 2 were joined by a conductive adhesive, and the case 4 and the electrode 7b, and the piezoelectric element 2 and the electrode 7a were joined by solder.
  • the electromotive force of the ultrasonic sensor manufactured as described above was 100 mV, and the electromotive force of the ultrasonic sensor after the thermal shock test was 98 mV. Therefore, the sensitivity retention rate of the ultrasonic sensor was 98%.
  • a disk-shaped lead zirconate titanate having a thickness of 2.8 mm and a diameter of 10 mm was used as the piezoelectric element 2.
  • the adhesive 3 an epoxy adhesive which is liquid at normal temperature and solidifies by heating is used.
  • a case 4 made of SUS304 having a thickness of 0.2 mm was used.
  • the first acoustic matching layer 15 a layer made of aluminum having a thickness of 1 mm and a diameter of 10 mm and having a through-hole having a diameter of 2 mm formed as a gap 8 was used. The distance between the holes is 200 ⁇ m.
  • a polymethacrylimide resin is foamed to form a molded article composed of closed cells, and a molded article having a density of 0.07 g / cm 3 is processed into a disc having a thickness of 0.8 mm and a diameter of 10 mm. What was used was used.
  • the assembly of the ultrasonic sensor 11 was performed as follows. First, the first acoustic matching layer 15 is immersed in the adhesive 3 at room temperature, and the case 4, the first acoustic matching layer 5, and the second acoustic matching layer 6 are arranged in this order from below. A load of 100 g was applied. In this state, the adhesive 3 is spread between the first acoustic matching layer 15 and the case 4 and between the first acoustic matching layer 15 and the second acoustic matching layer 6.
  • the adhesive 3 is solidified by heating at 150 ° C. for 60 minutes, and the second acoustic matching layer is joined from the case 4. Further, the case 4 and the piezoelectric element 2 were joined by a conductive adhesive, and the case 4 and the electrode 7a, and the piezoelectric element 2 and the electrode 7b were joined by solder.
  • the electromotive force of the ultrasonic sensor was slightly smaller, but was considered to be substantially equal.
  • the average density of the first acoustic matching layer is about 1.2 of the average of the PEEK resin and density 1.0 g / cm 3 of the epoxy resin having a density of 1.3 g / cm 3
  • the average density of the first acoustic matching layer is as large as about 1.6 g / cm 3, which is considered to be one of the factors.
  • the sensitivity maintenance ratio was 100%, which was further improved as compared with the second embodiment. This can be determined to be due to the fact that the difference in the coefficient of thermal expansion between aluminum and the case made of SUS304 is smaller than that of the PEEK resin, so that the shear force in the thermal shock test has been reduced.
  • a disk-shaped lead zirconate titanate having a thickness of 2.8 mm and a diameter of 10 mm was used as the piezoelectric element 2.
  • the adhesive 3 an epoxy adhesive which is liquid at normal temperature and solidifies by heating is used.
  • a case 4 made of SUS304 having a thickness of 0.2 mm was used.
  • the first acoustic matching layer 25 a material obtained by pulverizing PEEK resin and heating the powder having an average particle diameter of 100 ⁇ m while heating it to a thickness of 1 mm and a diameter of 10 mm was used.
  • the assembly of the ultrasonic sensor 21 was performed as follows. First, the first acoustic matching layer 25 is immersed in the adhesive 3 at room temperature, and the case 4, the first acoustic matching layer 25, and the second acoustic matching layer 6 are arranged in this order from below. A load of 100 g was applied. In this state, the adhesive 3 is spread between the first acoustic matching layer 25 and the case 4 and between the first acoustic matching layer 25 and the second acoustic matching layer 6.
  • the second acoustic matching layer is joined from the case 4 by heating at 150 ° C. for 60 minutes to solidify the adhesive 3. Further, the case 4 and the piezoelectric element 2 were joined by a conductive adhesive, and the case 4 and the electrode 7a, and the piezoelectric element 2 and the electrode 7b were joined by solder.
  • the electromotive force is slightly smaller than in the first to third embodiments.
  • the first acoustic matching layer has a porous structure made of PEEK resin and has a structure in which the voids are filled with epoxy resin, so that when the ultrasonic wave propagates, the acoustic impedance is similar, but the first acoustic matching layer is slightly reflected. It is considered that the efficiency is slightly reduced by repeating the above operation.
  • the sensitivity retention rate is improved as compared with the second embodiment.
  • the PEEK resin which is a part of the first acoustic matching layer, faces the case in the second embodiment, but is slightly affected by the shearing force due to the thermal shock.
  • the particulate PEEK resin faces the case in a point-contact manner, that is, almost entirely the adhesive made of the epoxy resin faces the case.
  • an ultrasonic sensor was manufactured by bonding the surface of the opening 8a of the gap 8 having a diameter of 400 ⁇ m as the case side, and evaluation was performed.
  • the electromotive force of the ultrasonic sensor manufactured as described above was 100 mV, and the electromotive force of the ultrasonic sensor after the thermal shock test was 60 mV. Therefore, the sensitivity retention rate of the ultrasonic sensor was 60%.
  • the electromotive force of the manufactured ultrasonic sensor was equivalent to that of the first embodiment.
  • the sensitivity retention was lower than that of the first example. This is because, when a linear elastic force generated in the case and the first acoustic matching layer is applied by the thermal shock test, the adhesive in the gap of the first acoustic matching layer has a component of a force in a direction away from the surface perpendicular to the surface direction. This is considered to be due to easy peeling.
  • an ultrasonic sensor was manufactured without providing a through hole, that is, a void in the first acoustic matching layer.
  • the ultrasonic sensor according to the first disclosure includes at least a piezoelectric element, a first acoustic matching layer bonded to the piezoelectric element, an adhesive bonding the piezoelectric element and the first acoustic matching layer,
  • the first acoustic matching layer has an opening that opens toward the bonding surface with the piezoelectric element, and a gap communicating with the opening, and the adhesive is filled in the gap.
  • the ultrasonic sensor according to the first disclosure has an anchor effect obtained by integrating the adhesive that bonds the piezoelectric element and the first acoustic matching layer with the adhesive that has solidified in the gap, and has an excellent effect. Durability can be obtained.
  • the first acoustic matching layer is a single layer, it is necessary to efficiently transmit the ultrasonic waves propagated from the piezoelectric element to the gas. , It is necessary to efficiently propagate the gas from the first acoustic matching layer to the second acoustic matching layer and from the second acoustic matching layer to the gas.
  • the acoustic impedance characteristics represented by the formula (1) it is necessary to suppress energy loss due to deformation of the first acoustic matching layer (high propagation characteristics) as characteristics required for the first acoustic matching layer. .
  • materials having high propagation properties are hard (high elasticity).
  • the material satisfying the formula (1) and having high elasticity is often a super-engineering plastic such as PEEK.
  • the adhesive that has been filled and hardened after filling into the gap is added to the acoustic matching layer in addition to the chemical bonding.
  • Mechanical bonding, ie bonding by the anchor effect As a result, a strong bond can be ensured even with poor adhesion (bonding by chemical bonding is weak).
  • the facing surface of the adhesive is relatively easily bonded to ceramics or metal.
  • the piezoelectric element and the first acoustic matching layer are not easily separated, and an ultrasonic sensor having excellent durability Can be provided.
  • the ultrasonic sensor according to the second disclosure has at least a metal member having a flat plate portion, a piezoelectric element bonded to one first surface of the flat plate portion, and an adhesive bonded to the other second surface of the flat plate portion. And a bonding agent for bonding the first acoustic matching layer to the flat plate portion.
  • the first acoustic matching layer has an opening that opens toward the bonding surface with the flat plate portion, and a gap communicating with the opening, and the gap is filled with an adhesive.
  • the ultrasonic sensor according to the second disclosure has an anchor effect by integrating the adhesive bonding the flat plate portion bonded to the piezoelectric element and the first acoustic matching layer with the adhesive solidified in the gap. And excellent durability can be obtained.
  • an opening area of the opening may be equal to or smaller than a cross-sectional area of the gap.
  • the ultrasonic sensor according to the fourth disclosure is the ultrasonic sensor according to any one of the first to third disclosures, further including a second acoustic matching layer adhered to the first acoustic matching layer with an adhesive, and the gap is formed by the second acoustic matching layer. It may have an opening communicating with the matching layer.
  • At least a part of the first acoustic matching layer may be made of resin.
  • the density of the substance after the liquid adhesive is filled into the substance having voids and solidified is an average of the density ratio of these substances.
  • the acoustic matching layer is the two layers of the first acoustic matching layer on the piezoelectric element side and the second acoustic matching layer laminated on the first acoustic matching layer
  • the density of the second acoustic matching layer is about 0.05 g / cm 3
  • the density of the first matching layer (the acoustic impedance largely depends on the resin because the speed of sound is small) is about 1 g / cm 3 .
  • This density corresponds to the density of a general resin.
  • the density of an adhesive such as an epoxy-based adhesive is about 1 g / cm 3 . Therefore, the acoustic matching layer by a resin, the average density becomes 1 g / cm 3 about the case where the density in the air gap is filled with the adhesive of about 1 g / cm 3.
  • the acoustic matching layer is made of resin, an ultrasonic sensor having excellent characteristics can be provided.
  • At least a part of the first acoustic matching layer may be made of an inorganic substance or a metal.
  • an ultrasonic sensor having excellent heat resistance can be provided by using a brazing material made of an alloy as an adhesive.
  • At least a part of the gap may have a substantially cylindrical shape.
  • the acoustic matching layer which is partially cylindrical, is suitable for production.
  • a through-hole between the surface of the acoustic matching layer, which has a substantially cylindrical shape and faces the piezoelectric element or a member bonded to the piezoelectric element and does not face the piezoelectric element corresponds to the gap.
  • the acoustic matching layer is made of a thermoplastic resin, such a shape can be produced by injection molding or by forming a through hole by machining a plate-shaped member.
  • the acoustic matching layer is made of metal, it is possible to form a through-hole by die-casting or machining a plate-shaped member.
  • the stress due to the difference in the coefficient of thermal expansion between the acoustic matching layer and the piezoelectric element or the member joined to the piezoelectric element is applied almost perpendicularly to the adhesive in the gap. Also, the effect of suppressing the troubles occurring at these interfaces is sufficient.
  • At least a part of the void may be obtained by molding a powder.
  • a member obtained by molding a powder has a void having an area larger than the opening.
  • the material that can be formed in such a wide variety includes inorganic substances, metals, resins, and the like. Accordingly, it is possible to form an acoustic matching layer having appropriate physical properties such as density, elastic modulus, and heat resistance temperature, and to provide an ultrasonic sensor having excellent characteristics.
  • the ultrasonic sensor according to the ninth disclosure is the ultrasonic sensor according to any one of the first to eighth disclosures, wherein the adhesive has an average density of 0.8 g / cm 3 or more and 1.5 g / cm 3 or less when cured. You may.
  • the density of the first acoustic matching layer (the acoustic impedance depends on the density because the sound velocity has a small resin dependency) Is greater than about 1 g / cm 3 , according to equation (1).
  • This density corresponds to the density of a general resin.
  • the density of an adhesive such as an epoxy-based adhesive is about 1 g / cm 3 . Therefore, the acoustic matching layer by a resin, the average density becomes 1 g / cm 3 about the case where the density in the air gap is filled with the adhesive of about 1 g / cm 3.
  • the density of the second acoustic matching layer is larger than 0.05 g / cm 3
  • the density of the first acoustic matching layer at which the maximum efficiency can be obtained as the ultrasonic sensor is different in each case of less than 0.8 g / cm 3. / Cm 3 or more and about 1.5 g / cm 3 or less.
  • the ultrasonic sensor according to the tenth disclosure may be configured so that, in any one of the first to ninth disclosures, after the adhesive is filled in the gap in a liquid state, the bonding is performed by curing.
  • the liquid adhesive in order to fill the gap of the acoustic matching layer with the liquid adhesive, if an excessive amount of adhesive is applied compared to the total volume of the gap, at least the applied amount and the total volume of the gap are applied to the surface of the acoustic matching layer. , A liquid adhesive corresponding to the difference is left. In such a state, when the acoustic matching layer comes into contact with the piezoelectric element or a member joined to the piezoelectric element, the liquid adhesive spreads on the interface between them.
  • the piezoelectric element or a member joined to the piezoelectric element is made of an inorganic substance or a metal, so that the joining is relatively easy. Therefore, by solidifying the liquid adhesive, it is joined to the piezoelectric element or a member joined to the piezoelectric element by a bonding force mainly based on a chemical bond, and the acoustic matching layer is bonded by a bonding force mainly based on an anchor effect. Joined.
  • the piezoelectric element or the member joined to the piezoelectric element and the acoustic matching layer are firmly joined, and an ultrasonic sensor having excellent reliability can be provided.
  • the ultrasonic sensor according to the present invention is suitably used for flow meters for measuring various fluids.
  • it is suitably used for applications requiring excellent durability in a high or low temperature environment as compared with room temperature.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
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  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
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  • Transducers For Ultrasonic Waves (AREA)

Abstract

L'invention concerne un capteur ultrasonore comprenant : un élément métallique (4) ayant une partie plaque (4a); un élément piézoélectrique (2) relié à une première surface (4b) sur un côté de la partie plaque (4a); une première couche d'adaptation acoustique (5) collée à une seconde surface (4c) sur l'autre côté de la partie plaque (4a); et un adhésif (3) pour faire adhérer la première couche d'adaptation acoustique (5) à la partie plaque (4a). La première couche d'adaptation acoustique (5) du capteur ultrasonore comprend : une ouverture (8a) qui est ouverte à la surface de la première couche d'adaptation acoustique (5) collée à la partie de plaque (4a); et un espace (8) contigu à l'ouverture (8a). L'adhésif (3) remplit l'espace (8). Un effet d'ancrage est obtenu par le durcissement de l'adhésif (3) dans l'espace (8).
PCT/JP2019/023823 2018-06-25 2019-06-17 Capteur à ultrasons Ceased WO2020004097A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
CN201980042135.5A CN112313968A (zh) 2018-06-25 2019-06-17 超声波传感器
EP19826265.1A EP3813385A4 (fr) 2018-06-25 2019-06-17 Capteur à ultrasons
US17/057,085 US20210208111A1 (en) 2018-06-25 2019-06-17 Ultrasonic sensor

Applications Claiming Priority (2)

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JP2018-119903 2018-06-25
JP2018119903A JP2020005027A (ja) 2018-06-25 2018-06-25 超音波センサー

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KR102371895B1 (ko) * 2021-09-14 2022-03-07 오순옥 앵커 인장력 측정장치 및 이를 이용한 앵커 인장력 측정방법
CN115097014A (zh) * 2022-06-21 2022-09-23 辽宁机电职业技术学院 一种用于薄板无损检测的超声波装置

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EP3813385A4 (fr) 2021-07-28
US20210208111A1 (en) 2021-07-08
JP2020005027A (ja) 2020-01-09
EP3813385A1 (fr) 2021-04-28
CN112313968A (zh) 2021-02-02

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